This invention relates to a structure of a color liquid crystal display panel. More particularly, it relates to a color liquid crystal display panel wherein a light-polarizing plate in which a color filter is integrated is used as a substrate. Color liquid crystal display panels are widely used for color displays such as watches, electric calculators, televisions, measuring instruments, automotive instruments, etc. and furthermore, they may be used for optical applications such as graphic displays, optical shutters, etc.
The conventional color liquid crystal display panels are shown, for example, in FIG. 4 (Unexamined Japanese Patent Application Publication No. 180525/84), wherein polarizers 411 and 412, protective films 421-424 for the polarizers, glass substrates 431 and 432, a color filter 440, transparent electrodes (transparent conductive coating) 451 and 452, a sealing material 460 and a twisted nematic liquid crystal layer 470 are indicated.
However, these color liquid crystal display panels have the following problems:
(1) The display quality is not stable over a long period of time, since the color filter is brought into contact with the liquid crystal layer through a very thin aligning film (not shown in FIG. 4), the diffusion of ions, molecules, etc. into the liquid crystal and discoloration of the color filter, results.
(2) The thickness of the color liquid crystal display cells can not be made smaller, since the substrate is made of glass. There is also a limit in making the display brighter due to absorption of light by the glass substrate. Further, the display is not clearly visible for a viewer unless he is directly facing the screen, since the light polarizing plate and color filter are separated by the glass substrate. Thus, such display panels have a narrow viewing angle.
(3) A rise time is required because the transparent electrode contacts with the liquid crystal layer through the color filter.
(4) There is a problem in adherence between the color filter and the transparent electrode and the yield is low.
(5) Workability is low because an additional step of bonding the light-polarizing plate and the glass substrate is required.
Another color liquid crystal display panel is proposed as in FIG. 5 of Unexamined Japanese Patent Application Publication No. 180525/84 in order to solve some of the above problems. In FIG. 5, there are indicated polarizers 511 and 512, protective films 521-524 for the polarizers, glass substrates 531 and 532, a color filter 540, transparent electrodes 551-552, a sealing material 560, a twisted nematic liquid crystal layer 570 and an intermediate thin glass substrate 580. In this display panel, the color filter is separated from the liquid crystal layer by placing the color filter on one side of the intermediate thin glass substrate opposite the liquid crystal layer and the transparent electrode on the same side as the liquid crystal layer. In this panel, the above stated problems (1), (3) and (4) are improved to some extent, but no improvement is seen for problems (2) and (5). There is a limit to the thickness of the intermediate thin glass substrate 580 and there is also a limit to the thickness of liquid crystal cell due to the presence of glass substrates 531 and 532. Furthermore, it requires additional steps such as bonding to the glass substrates, etc.
Another multi-color light-polarizing plate is proposed where a color filter is provided on a protective film for the light-polarizing plate in FIG. 6 of Unexamined Japanese Utility Model Application Publication No. 60106/82. In FIG. 6, there are shown a polarizer 610, protective films 621 and 622 for the polarizer 610 and a color filter layer 640. When a liquid crystal cell is made by bonding this multi-color light-polarizing plate to a glass substrate, the color filter can be separated from the color liquid crystal layer. Although there are improvements similar to those shown in Unexamined Japanese Application Publication No. 180525/84, they are not satisfactory yet. Furthermore, the viewing angle is smaller, since the transparent electrode and the color filter are faced through the glass substrate. On the other hand, when this light-polarizing plate is used as a substrate for a color liquid crystal display cell, the thickness of the liquid crystal cell can be made smaller and hence improvements may be made in making the display brighter, widening the viewing angled and increasing the workability. However, there are still the following problems, the color filter layer and the transparent electrode must be formed in contact with each other, and ions, molecules, etc. in dyes migrate into the transparent electrode to cause deterioration in performance; since a transparent conductive coating (electrode) is formed on the color filter layer by evaporation, a problem arises in adherence and the yield is reduced.
The inventors have done intensive research to solve these problems.